LED unit

ABSTRACT

An LED unit includes an LED and a lens receiving the LED. The lens includes a first light-incident face confronting the LED to refract the light emitted from the LED with a small angle into the lens, a second light-incident face surrounding the LED to refract the light emitted from the LED with a large angle into the lens, a light-reflecting face to reflect the light from the second light-incident face towards a top of the LED, a first light-emergent face to refract the light from the first light-incident face out of the lens, and a second light-emergent face to refract the light from the light-reflecting face out of the lens.

BACKGROUND

1. Technical Field

The present disclosure relates to a light emitting diode (LED) unit and,more particularly, to an LED unit having a lens which can produce aneffectively converged light beam.

2. Description of Related Art

LEDs, available since the early 1960's and because of their highlight-emitting efficiency, have been increasingly used in a variety ofoccasions, such as residential, traffic, commercial, and industrialoccasions. Conventionally, light directly output from the LED does nothave a desirable pattern; therefore, a light-adjusting element, such asa lens, is used with the LED to modulate the light pattern thereof.

However, a typical lens generally has a limited light-convergingcapability; that is, the light passing through the lens cannot beeffectively converged to have a small light-emergent angle. Thus, thelight pattern output from the lens may have a yellow annulus or shiningannulus appearing at a periphery thereof, adversely affectingillumination effect of the lens.

What is needed, therefore, is an LED unit which can overcome thelimitations described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present disclosure can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present disclosure. Moreover,in the drawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is an isometric view of a lens of an LED unit of the disclosure.

FIG. 2 is an inverted view of the lens of FIG. 1.

FIG. 3 shows a cross-section of the LED unit with the lens of FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIGS. 1 and 3, an LED unit of the present disclosure isillustrated. The LED unit includes an LED module 10 and a lens 30mounted on the LED module 10. The LED module 10 includes a printedcircuit board 12 and an LED 20 mounted on the printed circuit board 12.The printed circuit board 12 may be a MCPCB (Metal Core Printed CircuitBoard), a CPCB (Ceramic Printed Circuit Board) or other type PCBs whichhave good heat dissipation capability. The LED 20 includes aheat-conducting base 22, an LED die 24 mounted on a top of the base 22,and an encapsulant 26 covering the LED die 24 and fixed on the top ofthe base 22. The base 22 of the LED 20 is soldered on the printedcircuit board 12 to conduct heat generated by the LED die 24 to theprinted circuit board 12. In addition, the LED die 24 is electricallyconnected with the printed circuit board 12 via the base 22. The LED die24 may be an InGaN chip, an InGaAs chip, a GaP chip or other suitablechips which could generate visible light with a desirable color. Theencapsulant 26 is made by epoxy, silicon, glass or other transparentmaterials which have good light-permeable and water-proof capabilities.Phosphor may be doped within the encapsulant 26 to adjust the color ofthe light emitted from the LED die 24. The encapsulant 26 is shaped likea dome so as to collimate the light from the LED die 24 into a convergedbeam. The LED 20 has an optical axis I, around which the light emittedfrom the encapsulant 26 is symmetrical in a surrounding space.

Also referring to FIG. 2, the lens 30 is made from transparent materialssuch as PC (polycarbonate) or PMMA (polymethyl methacrylate). The lens30 includes a substrate 32, an optical member 34 extending upwardly fromthe substrate 32 and a flange 36 extending outwardly from acircumference of the optical member 34. The substrate 32 has a circularconfiguration with a rectangular window 320 defined in a bottom facethereof. The window 320 has an area similar to that of the base 22 ofthe LED 20 for receiving the base 22 of the LED 20 therein. A cavity 340is defined in the interior of the lens 30. The cavity 340 is locatedabove a center of and communicates with the window 320 to furtherreceive the encapsulant 26 of the LED 20 therein. The cavity 340 has ashape of a truncated cone. A diameter of the cavity 340 graduallydecreases from a bottom towards a top of the lens 30. An inner face ofthe lens 30 facing the encapsulant 26 of the LED 20 functions as a firstlight-incident face 301 of the lens 30 to receive the light emitted fromthe LED 20 with a small light-emergent angle (such the light b shown inFIG. 3). Another inner surface of the lens 30 surrounding theencapsulant 26 of the LED 20 functions as a second light-incident face302 of the lens 30 to receive the light emitted from the LED 20 with alarge light-emergent angle (such as the light a shown in FIG. 3). Thefirst light-incident face 301 is planar, and the second light-incidentface 302 is curved and slightly protruding inwardly towards the LED 20.The second light-incident face 302 has a curvature gradually decreasingfrom the bottom towards the top of the lens 30, ranging between 0.05mm⁻¹ and 0.08 mm⁻¹. The first light-incident face 301 and the secondlight-incident face 302 cooperatively form a light-incident face 300 torefract all of the light of the LED 20 into the lens 30.

The optical member 34 has an upwardly-expanding bowl shape. An outercircumference of the optical member 34 functions as a light-reflectingface 303 of the lens 30 to totally reflect the light transferred fromthe second light-incident face 302 towards the top of the lens 30.Alternatively, the light-reflecting face 303 can be further coated witha reflective layer (such as aluminum layer or silver layer) forpromoting light reflection. The flange 36 is located on thelight-reflecting face 303 and adjacent to a top of the optical member34. The flange 36 is for being pressed by a clip against the printedcircuit board 12 to thereby secure the lens 30 on the printed circuitboard 12. The light-reflecting face 303 is divided by the flange 36 intoa first light-reflecting face 304 and a second light-reflecting face305. The first light-reflecting face 304 is conical and graduallyexpands from the bottom towards the top of the lens 30. The firstlight-reflecting face 304 has a curvature firstly increasing and thendecreasing from the bottom towards the top of the lens 30, rangingbetween 0.02 mm⁻¹ and 0.06 mm⁻¹. The second light-reflecting face 305 isvertical and has a zero curvature.

A top face of the optical member 34 is concaved downwardly to form aconical second light-emergent face 308. The second light-emergent face308 directly connects with the second light-reflecting face 305. Aprotrusion (not labeled) is protruded upwardly from a central area ofthe top face of the optical member 34. The protrusion has a flat topface and a curved circumferential face continuous from the flat topface. The flat top face and the curved circumferential face of theprotrusion cooperatively form a first light-emergent face 307 of thelens 30. The first light-emergent face 307 mostly takes charge for thelight transmitted from the first light-incident face 301, the secondlight-emergent face 308 mostly takes charge for the light totallyreflected by the light-reflecting face 303, to thereby refract nearlyall of the light from the LED 20 out of the lens 30 within a smalllight-emergent angle. The first light-emergent face 307 has a curvatureranging between 0 and 0.9 mm⁻¹, and the second light-emergent face 308has a curvature ranging between 0 and 0.12 mm⁻¹. The first-emergent face307 and the second light-emergent face 308 cooperatively form alight-emergent face 306 to refract the light within the lens 30 towardsa place above the lens 30.

Being adjusted by the first light-incident face 301, the secondlight-incident face 302, the first light-reflecting face 304, the secondlight-reflecting face 305, the first light-emergent face 307 and thesecond light-emergent face 308, the light emitted from the LED 20 couldbe effectively converged within a small angle, thereby preventing aperiphery of a light pattern output by the LED 20 via the lens 30 frombeing yellow or shining.

It is believed that the present disclosure and its advantages will beunderstood from the foregoing description, and it will be apparent thatvarious changes may be made thereto without departing from the spiritand scope of the present disclosure or sacrificing all of its materialadvantages, the examples hereinbefore described merely being preferredor exemplary embodiments.

1. An LED (light emitting diode) unit, comprising: an LED; and a lensmounted on the LED, the lens comprising a light-incident face adjacentto the LED, a light-emergent face remote from the LED, and alight-reflecting face between the light-incident face and thelight-emergent face, wherein light emitted from the LED with a smallangle is refracted by the light-incident face and the light-emergentface out of the LED unit, light emitted from the LED with a large angleis sequentially refracted by the light-incident face, reflected by thelight-reflecting face and refracted by the light-emergent face out ofthe LED unit; and wherein the light-reflecting face comprises a firstlight-reflecting face and a second light-reflecting face having acurvature different from that of the first light-reflecting face;wherein a flange is protruded outwardly between the firstlight-reflecting face and the second light-reflecting face; and whereinthe light-emergent face comprises a first light-emergent face and asecond light-emergent face surrounding the first light-emergent face,the first light-emergent face comprising a flat top face, the flat topface of the first light-emergent face being located higher than theflange and lower than a joint of the second light-reflecting face andthe second light emergent face.
 2. The LED unit as claimed in claim 1,wherein the first light-reflecting face is conical and gradually expandsupwardly along a bottom-to-top direction of the lens.
 3. The LED unit asclaimed in claim 1, wherein the curvature of the first light-reflectingface ranges between 0.02 mm⁻¹ and 0.06 mm⁻¹.
 4. The LED unit as claimedin claim 1, wherein the curvature of the second light-reflecting face is0.
 5. The LED unit as claimed in claim 1, wherein the firstlight-reflecting face and the second light-reflecting face arediscontinuous from each other.
 6. The LED unit as claimed in claim 5,wherein the flange is located adjacent to a top of the lens.
 7. The LEDunit as claimed in claim 1, wherein the second light-emergent facedirectly connects the second light-reflecting face.
 8. The LED unit asclaimed in claim 7, wherein the first light-emergent face comprises acurved circumferential face surrounding the flat top face.
 9. The LEDunit as claimed in claim 7, wherein the second light-emergent face isconcaved downwardly to have a conical shape.
 10. The LED unit as claimedin claim 7, wherein the second light-emergent face has a curvatureranging between 0 and 0.12 mm⁻¹, and the first light-emergent face has acurvature ranging between 0 and 0.09 mm⁻¹.
 11. The LED unit as claimedin claim 1, wherein the light-incident face comprises a firstlight-incident face facing the LED, and a second light-incident facesurrounding the LED.
 12. The LED unit as claimed in claim 11, whereinthe first light-incident face is flat.
 13. The LED unit as claimed inclaim 11, wherein the second light-incident face is protruded towardsthe LED.
 14. The LED unit as claimed in claim 13, wherein the secondlight-incident face has a curvature ranging between 0.05 mm⁻¹ and 0.08mm⁻¹.
 15. The LED unit as claimed in claim 11, wherein the lens has awindow defined in a bottom thereof and a cavity defined in an interiorthereof, the window communicating with the cavity, the window and thecavity together receiving the LED therein, the first and secondlight-incident faces being formed by the lens defining the cavity, thecavity having a shape of a truncated cone.
 16. The LED unit as claimedin claim 1, wherein the flat top face of the first light-emergent faceis located at a center of the light-emergent face and aligned with theLED.